A cerium-based abrasive including cerium-based particles as a principal component has extended its use quickly based on an outstanding polishing effect. Now, it is used for not only a conventional glass polishing use for optics, but also fields of glass polishing for liquid crystal magnetic recording media such as a hard disk, and manufacturing of electronic circuits including LSI.
Generally the cerium-based abrasive is manufactured by following methods. That is, after material is slurried, wet pulverized and treated with mineral acids etc. if needed, chemical treatment is performed through hydrofluoric acid, ammonium fluoride, etc. The obtained slurry is filered, dried and roasted, and subsequently, pulverization and a classification are performed and abrasive particles having a desired particle size are obtained. Moreover, as a raw material of the cerium-based abrasive, rare earth raw materials, such as rare earth carbonate, rare earth hydroxide, and rare earth oxalate, or rare earth oxide raw materials obtained by calcinating these materials are used. These rare earth raw materials are usually manufactured by removing some rare earths (Nd, Pr, etc.), radioactive elements, etc. by chemical treatment from bastnaesite based rare earth raw materials or cerium containing rare earth raw materials. Moreover, usually the cerium-based abrasive is used in a state of slurry dispersed in dispersion media, such as water.
Then, it is required that a high polishing velocity might be demonstrated as a premise to cerium-based abrasive slurry, and further that manufacture of polished face having outstanding specular surface property might be enabled. This is a characteristic required not only for cerium-based abrasives slurry, but for general abrasives. On the other hand, not only excellent polishing characteristics, but improvement in other properties are required.
As one of new characteristics required to cerium-based abrasive slurry, adhesion property of abrasive particles onto a surface of materials to be polished may be mentioned. This relates to highly precise polished face formation to be on demanding in a field for which the cerium-based abrasive is used. That is, if the abrasive particles in the abrasive slurry has a high adhesion, the abrasive particles will remain on a material to be polished surface after washing. And the residual abrasive particles cause a blemish depending on subsequent handling, and will injure an accuracy of a polished face as a result. And for example, when a material to be polished is a substrate for hard disks, such existence of residual particles makes a factor that deteriorates flat and smooth property of the substrate, when a magnetic substance is vapor-deposited after polishing.
On the other hand, in examples of examination on conventional abrasive or abrasive slurry, many examples exist in a filed about an improvement of polishing properties. However, sufficient solution is not yet proposed and coexistence between polishing properties and dispersibility is not achieved in adhesive improvement of abrasive particles in abrasive slurry.
The present invention is made in view of the above described actual circumstances, and aims at providing a cerium-based abrasive slurry in which abrasive particles do not adhere to a polished face after polishing, and formation of a blemish is not given after polishing, but a highly precise specular surface is maintained while having outstanding polishing power and outstanding polishing accuracy. Moreover, a method for manufacturing such a cerium-based abrasive slurry is also provided.